Sound-locating apparatus



mm 29,1927. 1,622,594 L LANGMUIR SOUND LOCATiNG APPARATUS 7 sheets s'neet 1 Filed May 51, 1919 Inventor 1rvin%Langmuir;

H is Attorngg? March 29 1927.

l. LANGMUIR SOUND LOCATING APPARATUS 7 Sheets-Sheet 3 Filed May 31, 1919 maw vw m we b March 29, 1927.

\rvmg g Hi A nrn l LANGMUIR scum: LOCATING APPARATUS Flled May 51, 1919 'r Sheets-Sheet 4 I Inventor-z Lan mun;

March 29, 1927. 9

- I. LANGMUIR SOUND LQCATING APPARATUS Filed May-31, 1919 '7 sheets -she et -5 lnventor z "223 9am l-l isALtorne M web 9 192?.

a 2 l. LANGMUIR SOUND LOCATING APPARATUS Filed May 31 v 7 Sheets$heet e Inventor:

Irvin March 29, 1927. 1,622,594

I. LANGMUIR 3 SOUND LOCATI NG APPARATUS Filed May 31, 1919 7 Sheets-Sheet '7 I 7n- 35 3s Inventor: Irving Langmuir;

His Annbrng- Patent'ed Mar. Zti;

entrain stares savanna-o IRVING naneizruxn,

orsonnnncrany, nzew'ronn, .essrenon TO snnnnet deacon-re" commas, a. coaronarron or new YORK.

socrrn-tooarme ArPAnarUs.

Application filed May :51,

My invention relates to the detection .of sound and thedetermination of the direction of its source, and more particularly'to the accurate determination of the direction of b the source of faint sound transmitted through a liquid'mediunf, such as water. I

' The direction of a source of sound is estimated or judged principally by the binaural effect produced when sound waves in from the source" aflect both ears of the listener. This edect, whichdepends mainly 011- the difference in time of arrival of corresponding sound waves at. the ears-of the listener, is observed even when sound is brought to the ears through tubes such as the tubes of a stethoscope. Corresponding sound waves which do not reach both ears simultaneously produce the impression that the source of sou-nd'is on one side or the other,

and the listener is able to make an app'roxi-' "mat-e determination or estimate otits direction. Corresponding sound waves which arrive at both ears-simultaneously produce a sharply defined impression or sensation that the source of sound is directly in front of the listener. Where the sound waves are brought to ,the ears through two separate andQdistinc-t tubes the relative time of arrival of the. sound waves at the ears can be varied p by adjusting the relative lengths of the 'two tubes. The listener, by makinguse .of this .well marked sensation or impresionprodue-ed when tlleSOUnll waves arrive atv both ears simultaneously can determine with a high. degree of accuracy when both sound v 'waves arrive at the ears at the same instant One object of my invention is 'to provide:

' apparatus in which sound collectors are placed at whatever points are most suitable,

40 even at great distances from the listener and from one another if desired, and the; soiinds I from the collectors transmitted to a simple and compact compensator at any point conve'nient for the listener. Another object is to provide a sound detecting apparatus having a greater range'and better adapted for the detection of faint sounds than those heretofore used. .A further object is to provide co pact and eificient and in which all connections are made to stationary parts. Another ob ect 1s'.1n general 'to provide'iman. improved compensator which is very- 1919. Serial No. 300,807.

proved apparatus for determining the 'dibesubmerged in deep ,quiet water by means of a submerged float or may be mounted on the hull of the ship, either inside or outside. In addition the sounds may be magnified to any extent desired, thereby facilitating detection of faint sounds. To enable the listener to bring the sounds from the two sound collectors into phase so they will reach both ears at the same instant, I'combine with the two telephonic sound collectors some means to i for varying at will the phase relations of the sounds transmitted by the collectors. This can be done by varying the phase relation of the telephonic currents in the two telephonic sound collectors, or by alteringv so th e time requiredfor sound to travel from either sound collector to the ear. A. convenient way to alter the time of, travel .of the sound is-to alter the length of the path along which the sound waves travel. To do this I. as prefer to use an air-compensator through] which the sounds from the two telephone receivers travel along separate and distinct air paths, and by which the relative lengths ofthe two air paths are varied. The setting so of the compensator necessary to bring the sounds from the collectors into phase so as to obtain the equalization of the hinaural effect. indicates the angle which the sound wave makes'with a line joining the colleotors, and therefore the hearing or direction of, the soupre of the sound may. be read directly on a scale; attached to the compensator;

The con'ipensator is .preferably made'in the form of two concentrically mounted cooperating disks rotatable with relation to each other. one provided with two concentric groov s ioined at their ends, and the other.

with two projections which fit into the grooves and divide them into separate and distinct U shaped paths along which the sound travels through the compensator .to the ears of the listener. Rotation of one disk of the compensator on the other short ens one air path 'andlengthens the other.

To determine the true bearing of the source of sound I use at least three sound collectors I set out of alignment, and provide means for leading the sound from any two collectors to the ears of the listener. With each pair of collectors two bearings are obtainable, one

ing is the same with every pair of collectors while the false bearings are all different.

The novel features of my invention are pointed out with greater'particularity in the appended claims "butthe invention itselfwill best be'understood by reference to the following specification and the accompanying.

drawings -m which, merely .for purposes of illustration, I have shown one of the various forms in which my invention may be embodied and in which Fig. l is a per- 'spective view of the exterior of the compensator box; Fig. .2 a cross section of the com pensator box along the line 22 of Fig. 3,; Fig. 3 a longitudinal section of the com.- pensa tor box along the line 3 3. of Fig. 2;

Fig. 4 a perspective viewshowing thebottom disk of the compensator with the top disk removed; Fig. 5 a perspective view of the under side of the top disk of the compensator; Fig. 6 a perspective view of the under side of the lid of the compensator box showing the two receivers; Fig. 7 a longitudinal section showing an adjustable bearing forthe top disk; Fig. 8 a longitudinal section of the attachment plug by whichthe electrical connections are made from the microphones to the compensator; Fig. 9 a plan view of the scale cover by which only the proper scale is exposed to view; Fig. 10 'a. plan View of the scale disk showing the three scales on it; Figs. ll, 12 and 13 are plan views of the scale cover and scale disk in three diflerent diagrammatic View; Figs; 15 and 16 diagrams to illustrate a principle used in my invention; and Figs. 17, 18 and. 19 diagrams illustrating three different positions of the parts of the apparatus. zontal sectional view of a'special form compensator Fig. 21- shows a purely acoustical system. v p

In the particular embodiment of my invention illustrated in the drawings the compensator is mounted in a compensator box 20 which. also contains enough of the electrical equipment associated with the compensator to make a self contained unit which can at will be connected to or disconnected from the transmitters. The 'compensator box has a pivoted lid 21 with a] lifting knob positions; :Fig. 14:. 1s a,

Fig. 20 is a hori v of the inner groove to the outlet 40. If the 'top assets;

cover 2a with a window for exposing the compensator scale.

As best shown in which-1s sound insulated from the cup23 by felt or similar sound insulation 25, com

prises ahorizontal bottom disk 26, witha perpendicular. center post 27 and a cooperating top disk 22: rotatable on the bottom disk about-the post 27 by means of a handwheel Set into the lid-is a metal cup shaped I Fig. 3, thc co'mpensator,

29, which preferably has a smooth rim so that the operator will not know the position of the diskby the positionof the handwheeli A scale plate 30 on the top disk visible through the widow in the made of bronze-and their abutpreferably accurately. I

ting faces must be fitted very prefer to grind them to each other finishing over by lapping with a very soft abrasive,

as any grit embedded in the face'of either disk will spoil the device.

To make two separate air paths which can be varied in length by relative rotation of the plates, the top disk has two concentric g y and connected at their ends by cross channels 33 which make a gradual bend to avoid reflection of sound and are of the same cross section asthe' two grooves. convenience in manufacture the grooves may be cut as complete "circles and then filled between the cross'channels 33 with parti-. tions 34: of soft metal such as Babbitt metal or lVoodsmetal poured into place after the two blocks rooves 31 and 32 formingarcs of circles I cover 24: shows the position of the top disk. The two disks are As a matter of metal, which make an airtight sliding fit in the grooves 31 and Two inlet ports,37

and 38 on opposite sides of the block 35,

and two outlet ports 39 and 40 on opposite sides of the block 36 provide, inconjunction with the grooves and blocks, two distinct air paths through the compensator, one extending from inlet 37 to one end of the outer groove, through the cross channel and back tothe outlet 39, the other extending fI'OIll' inlet 38 to the other end of the outer groove, through the cross channel. and back along and forth. By using two concentric grooves each an path is refiexed or bent back so. that I it is 'U-shaped and any movement of the disks affects the length of both legs of each air sire I may use several pairs off'grooves, the

path. Where a very great range is detwo U-shaped air pains formed by each pair being connectedto the corresponding U- shaped air paths formed by the next pair of grooves-and so on, so that each air path through the compensator has several. U,

shaped portions instead of only one, and all of the U-shaped portions of one air path and er are the grooved passages through the compensator, and 37, 38,39, 3t 38", 39" and 40 are the ports therefolz- A wide range of adjustment is obtained, yet

I a the device is very compact. Another very on billiard tables is suitable' compensator.

marked advantage is that both the inlet and outlet ports are in. the stationary bottom plate.

In the; particular arrangement shown a.

casting-41 attached to the bottem plate is provided with inletc'hannels 42. in register with the inlet ports to admit the sound to the compensator and with outlet channels 43 in register with the outlet ports to carry away the sounds which emerge from the into an outlet tube lined with felt toprevent reflection of sound. The felt such as is used The felt lin- 'ing 44 ofthe outlet tubes is b acked'by thin sheet metal to hold it insha'pe, and tapers tofoim a conical felt tube leading to stethoscope nipples 45 over which stethoscope tubes provided with ear tips are slipped to.

"tube is 'veny short, or a, vent hole is madein provide two air paths of exactly equal length to carry the sound from the compensator to the earsof the listener.

As the sounds to be detectedfmaybe mingled with'other sounds and with noises from the l1stener soWn shlp and sometimes are so faint that any distortion or interfer-- ence will render them unrecognizable, the compensator must change thelengthsof the two air paths forthe sounds without male ing any appreciable noise or distorting the sound waves, and without leakage from the sound passages, as very slight leakage be tween themdecreases the sharpness of the effect.

Very slight friction between metal to metal surfaces in the compensator will produce"? loud grinding and roaring noise i on when the'compensator is moved, and sufii oient leakage to cause trouble will occur 1111- less the passages are air tight. To keep the compensator quiet and tight I use between the disks a thin film of lubricant, such as castor oil, which prevents metal to metal contact/hut permits noiseless movement of the-disks and seals the grooves'again st'lealfrage, and I also provide means for accui rately adjusting the clearance between the plates. Y r

Each outlet channel opens The particular formof clearance'hdjust-- .ing device which I plireferis illustrated in the drawings, particu arlyin Figs. 1, 3, and. 7; 'The upper plate is supported on an ad-,

justable ball hearing which comprisesa ball flfl 46 resting in aslight cup 'or depression in" the upper end of the post 27. The lower end of an adjusting plug-47 'screwthreaded into the fhandwhcl '29 rests on the ball 46.

.li'y rotating the adjusting screw 47 all; or part of the weight of the top'.disk can be carried on the ball 46, and the clearance betweenthe top disk and the bottom disk regulated to a nicety. Y Asthe compensator is air tight shorten- .80 mg one airfipassiage and lengthening thev other" causes pressure variations which produce an unpleasantefi'ect on the ear drums of the listener and also interfere with listeniug. To minimize thee pressurechanges without appreciably weakening the sound wavesor 'alttl'lllg their characteristics, I pro vide for each 'airpath a. tubular relief rent 48, best shown in Fig. 3,, of such a bore that it relieves the pressure and of such a length 0 that practically none of the sound waves escape through it I have found by experi' inent that a vent tube about two inches long and" with a bore about lIlC l1 WlllT8llV6' practically all of the objectionable pressure variations without modifying the sound waves The columnof air in'the ventztube has so much inertiathat it is but little a-ffected by the comparatively rapid var ations Pressure due'to sound Waves, but yields 9 to the slow sustained pressure produced when the compensator is moved. If the vent a thin walled tube, the airin the vent yields I to the pressure variations of the sound waves,

and sound is lost. In addition, resonance effects are produced and the quality of. the

sound altered. i

.To catch surplus oil, pads of ab orbent material may be placedat the lower ends of the inlet andoutlet channels, {A convenient Way of holding this material is in removable j l soundcollector t ithg compensator-by ing, because the compensator itself ihtro-.

duces no disturbing noises and does not alter:

in any way the characteristics of-the sounds" pa sing through it. w i I f- In the en'ibodime ut illustrated the sounds are delivered to thetwoinlet channels 42 1w:

two telephonic receivers A9 and 5Q connected? to' submerged j transmitters. .,The'se receivers? must be connectedsothat their polaritywilli be the same, otherwise a compressional sound 3 rarefactive sound wave in the other path,

and serious errors will be produced.

By my invention three transmitters are used and to connect at will any two ofthese three transmitters to the two, 'receirers l provide. means, such as a transfer. switch, for controlling the'electrical connections. The particular transfer switch illustrated. is mounted, as shown in Fig. 3, inside the cas- 'ing 23, concentric with the compensator, and

comprises an upper ring, consisting ofth'ree insulated segments 51, 51 and 51, a middle ring 52iconnected to receivcr-49, a1'1d a lower ring 53 connected to the other receiver 50, these rings being mounted mi but insulated from the wall of the casing. A} set of brushes 5 1 out 55 for connecting .the' segments to the middle ring and another set of brushes '56 and 57 for connecting the segments to the bottom ring are mounted'on brackets, 58 of a'brush'h'older ring 5% rotatably mounted 'on'an annuluriboss 60' on the bottom of the casing A handle or pointer 61 immediately beneath the handwhccl of the compensator and easing moves a plate or calecovcr (52 which, thrcugh pins (53 entering slots 64 in the brackets 58, shifts the brush holder ring 59 as the handle 61 is moved, so'that the pointer .01 handle 61 shows the position of the trans 'l'cr switch. The pins 3 and :{lots 6-1 are sorelated that the parts cannot be assembled in wrong relation. The scale-cover (32 moves in synchronism with the brush holder ring, and exposes the proper one of the three scales A, B and C on the scale plate 30. A

The connections of the transfer switch and of the electrical devices mounted in the compensator box will best. be understood from F1g.'14 which is a diagram of the electrical COIlIl0'('l10I1S to the three microphone transm tters'a, b and a. l The transfer switch is shown position to the receivers 49 and 5t), whilejtransmitter 'c isidle.

to connec' transmitters 'a and Z) The three segments 51, 51 and 51 of the transfer switch are connected through condensers 65 65 and 65 to contactbrushes 66, G6"- and (36 and also through reactances 67, tfi and 67 ton common terminal of two supply batteries 68 and ($9. Either one of these batteries can be used at will by operating an interchange switch 70, which is connected, through an operating switch 71 shunted by a. conden'er 72, to -a contact brush 73. For convenience in measuring'the potential of the supply battery, I provide. avoltmeter V. .To-illuminate the scale I'may use a scale lamp '74 lighted from a lamp battery 7 5 by means of a push but --Dircct current ton 76-'on the lid 21 of the compensator box. All of the parts of the 'device 'above described are contained in the compensator box 20 and form a compact portable unitwhich may be above the-cover of the connected to and disconected from the transmitters at will.

The electrical connections to the three mi crophone transmitters may be made in various ways, plug 77 adapted to be inserted in the compenstitor box and to cooperate with the four contact brushes in the box As shown in Fig. 18 and illustrated diagrammatically in Fig.14, this plug?! has an-insulate'd conducting-sleeve 78 and three insulated conducting rings 79?, 79 -and 79. 5 The plug is connected through to the three microphone transmitters a, b and e, each connected at one terminal through a conductor of the cable to the conducting rings '19, 79 and 79, respectively, and at the other terminal through a common connection 81 and the fourth conduca four-conductor cable but. I- prefer to use an attachment r lVhen'the attachment plug is. inserted in the boxtlie conducting rings 79, 79 and 79- are connected, respectively, to the contact brushes 66, 66 and-66, and. the sleeve 78 is connected to the contact brush 73. 4

The three microphone transmitters or sound collectors'a, band 0 may be of any desired type which is relatively non-resonant. Rubber and similar material may be used to advantage, and l prefer to use a trai'ismitter of the inertia type mounted one soft rubber diaphragm-which forms one wall ot-a closed chamber containing the microphone. A suitable type isshown in my Patent No. 1,475,190 granted Nov. 7, 1923.

The transmitters aremounted at the anglcs of an equilateral triangle, and may be placed at: any convenient distance from each other. j Good results, have been obtained where they were as close g as far apart as .50 feet The further they are apart. the more accurately can the dibe determined. The transmitters rection placed on a frame or tripod placed can be tance from the compensator on shore can be fioat which keeps them 50 or 60 feet below as 18 inches, and 105 on the bottom of the sea at any desired dis-' the surface where the water is comparatively quiet; maybe towed from the ship,

or maybe mounted in water or oil tanks to collect sound vibrations transmitted from the sea water through the ships plating to the water or oil in the tanks. Asthelocation of the transmitters does not depend on that of the compensator,

andthe compensators can be located in the best positions without reference to" each other;

from the supply battery flows through all of the micro hone transmitters through a circuit containing the .reactances 67", 67" and 67. When-the .voltage drops below the proper amount the the transmitters circuit become stable.

shifting switch 70 should be iised to'connectii in the other supply battery. Before shitting from one supply battery to the other, or be-' which occurs and causes the. microphone to:

lose' its sonsitivencss ii the supply battery circuit is broken at any other poiht, Itis often desirable to arrange the cir-' c'u'its so that when any two of. the microphones are connected ,to the receivers the third. microphone is conncctedthrough a'resistan'ee, resistance and inductance, equiv-i ale'nt to that of one of the" receivers; so, that the circuit through each microphone'l's." maintained practically constant. regardless of the position of ,the transfer switch. One

'way of doing this is to provide the'bru'sh holder ring 59. with a brush 82 connected through inductance and capacity to the terniinal ot' the supply ba'ttery,'as indicated diagrammatically in Fig. 14. ln pia'ctice the connection may conveniently be made In this manner Iavoid'th'e change in sensitive-- ness which sometimes occurs when a microphone is first switched into circuit, as the sensitiveness of the microphone sometimes changes for few minutes after it is first put in circuit until the conditions in the The mode of operation of my invention" will he better understood by first considering the diagrams shown in Figuresw and 16, which. illustrate its general principle; Referring}; first to Fig. 15, let D and E be two transmitters submerged in the water and connect-ed as pre ."iously.describcd to the two receivers 49 and 50.- in client the listener at the compensator faces the point T, with his leftear 'hearingrsound from transmitter l3 and his rig-ht ear, hearing.

sound from transmitter E. Let the hear ingzs be taken on a scale of which the zero point -IS on the line QT.

A sound wave in the water; spreads in a circle from its source, but in practice the source is always so far away that when the sound wastearrives at the transmitters, andl] the sound is in the form of aLplane vare whose plane is perpendicular tothe hearing: or lirection of its source. Supposea sound wave originates at a source T which is some-distance away. .Tllls wave, traveling'froni 'l to 0 with its plane perpendicular to the line (l'l will reach both transmitters the same instant. producing corresponding sounds from both, receivers at the same instant. If the compensator is set inits HiltllillC position, as indicated diagrammatically int-lg. 14;, so that both of the air paths through, it are of the same length, the sounds.

.zero or ISO'deg'rees, but he'does not emitted by the two receivers .at the-same instant will reach both ears of the listener at. the same instant, and hewill re'ceive the impression that the source of sound is directly in front of him. L 70 However, a precisely similar efi'ect will v be produced by a sound originating at '2. source because a sound. wave'from the "latter source would also reach'the two transmitters-D and at the same instant. Un- 7s der the conditions just assumed the listener knows that the source of sound is somewhere on the line TS, and that its bearing is riglhcr- 'whi'ch bearing is the'true one.

Now assume that the sourceis at X.

Let the'plane of the sound waves, which is perpendicular to the line OX, be rep resented at the instant the Wave reaches the- "transmitter E by the full line"Em.-

The were will reach the other "transmitten D some time later, as it still has to travel t l-i c distance De, which depends upon the angle the line OX makes with the line DE, If this distance Dar, can be measured the bearing of the source will be known As the speed of the sound wavejin the medium in which it; travels is known, and 'the time at which the sound wave reaches transmitter E .dilfers from that at which it reaches transmitter Dby the time required for the sound to travel this dis tance Dm in water, a. measiireme'nt of this time difference or interval will give the dis tance Dr, and therefore the hearing of the 1 9 source of sound. When the listener hears the sound from transmitter E first' he gets the impression tha'tthe sonrceis somewhereto the right of him. By turning the-compensator to the right, that is, clockwise, it '5 may be set to-bringtthe sound romboth transmitters to both ears at the 5 ue instant. Theextentofmovement of the compensator measures :the time interval due to the distance D03 and therefore its'setting indicates 1v the distance Da:. The sound wave travels {ilDOUh'il times as fast inwater as it does in air) Suppose the ath'inair over which the sound from transmitter E reaches the; listeners right ear is lengthened by an amount, equal to of the distance Dr. The sound will require just. the same time" interval to travel this extra length of bath. in air that it requires to travel the distance Da; in/ water. consequently the sound from transmitter E traveling over thelengthened air-{bath will reach the right car of the liseneryat thesame instant as the sound from. transmitter D reaches his left sin- The proper lengthening of the air-,path is brought about by moving the compensator until glll'ie'listcner gets the impression that the source of sound is directly in front of him. As the maximum time interval bei t at least tween the sound from the two transmitters occurs when the sound wave comes from a 4 4 of the distancefbctween the two transmitters to compensate for the time required for a sound wave in Water to travel from one transmitter to the other. extent of movement of the compensator depends upon the time interval between the' sound from-the two transmitters, and therefore. upon the distance D e, the setting of the compensator indicates the bearing of the source of sound, However, with this same setting of the compensator the same eflect is produced on the listener if the sound wave comes from a source \V, because the sound wave from this latter source would also striketransmitter E before it strikes the other transmitter D "and at the instant it strikestransmitter E it must 'go a distance Dw before'itstrikes the other transmitter D. As this distance Dw is equal to the distance D00, sound from either source X or source WV produces the same eifecaso when the listener gets the impression that the source of sound 'is directly in front of him he can not tell whether the bearing X or W is the true one. o

"For the same reasons sound from either source'Z or source Y will give the same et- Dy are equal, one setting of the compensator -will give the same effect from either source.

, mitters be swung feet.

a distance D's before striking the other transmitter, and when a sound wave from a source 7 Y strikes transmitter IE, it also'has to travel a distance Dy before striking the other transmitter D. As these two distances D2 and There is no ambi 'uity' if the source is in inalignment with t' e transmitters D and E but the bearing of such a source cannot be read very' accurately, because a very slight error in setting the compensator makcs a large errror in the bearing. 1 j I The bearing as read upon the scale of'the compensator depends upon the an ular rela 'tion of the two transmitters to t e -hne of reference. For example, let. the two transindicated in F1g.. 15 about the point Gas :1. center through an arc of 120 into the-position indicated in Fig. 16. Let the source I T is directly'in front of the listener, and the scale of the compensator must also be difi crcut, so as to read zero sound from the source T. The other r 'uu'ce S, which will Asthe;

When a sound wave from source Z- strikes transmitter E, it still has to travel right .ear of the listener.

clockwise from the positions give the same effect with the compensator in this position, wil-l' h'ave on this compensator scale a bearing of 60 de recs.

The operation of my invention will bestbe' understood in connection with Figs. 17, 18

19, which show diagrammatically the electri-.

cal connections and the-three different positions of the transfer switch and the compensator. In these diagrams the line of-reference is assumed to be the same as in Fig. 15, perpendicular to the line joining the transmitters a and b. with zero of the azimuth circlea'bove this line The source of sound which is. to i be located is assumed to be T and the bear- 'ing of this source of sound is assumed to be 50 degrees.

For conveniencethe operation of locating the source of sound T will'be begun with the transfer switch in the C position, in which it is shownin Figs. 1, 2, 3 and 14; Inthisposition' transmitter a is idle, and transmitters a and I) are connected to receivers 49 'and 50, respectively. In effect the listener is facing transmitter 0. The scale cover is in the position shown in Fig; 12, exposing the C scale only. i

The sound wave from the source T M11 7 travel .in the water towardthe'transmitters 1 with its crest perpendicular to the line OT. This sound wave first reaches transmitter Z2 and sets up currents which flow,- through the connections shown, to receiver 50 which thereupon emits a sound corresponding to the sound wave In the water. This sound wave '1n a1r emitted by the receiver '50 enters the compensator through the inlet channel 42 and inlet port 38, travels along the right hand air path in the compensator to the outlet port 40 and outlet channel 44, and thence to the connection with Fig. 15 the sound'wave in water has not at this time reached transmitter a, but will reach it later. The listener wheel to theright, that is, clockwise, into As explained in I 1 receives the impression that the'source of" sound' is to the right. He turns the hand the position indicated dia rammatically ini Fig. 17. This movement oi the compensator lengthens the right hand air path and shortens the left hand air path and thcsourcc of sound thus apparently moves toward the leftnntil it scemsto be directly in front of the l stener. In this position of the compensator the sound whic 1 starts early from the receiver 50 and travelsovcr the long"- right hand air path arrives at the right ear of the listener at the same instant thatpr'n'ciples explained in Fig will show that the bearing ofthe other source F, or the false hearing OF, is 130 degrees. The scale is graduated to read both degrees and 1-30 grees for this setting of the'cornpensator, an the listener'knows that the source of the sound to which heis listening is onone of these two "bearings, but he doesnot know.) which .is the true hearing and which is the false bearing. He, therefore, reads the position of the compensator-on the 0 scale as either 50 degrees or-13 0 degrees.

The next step is to shift. the transfer switch to another position, and for convenience we will assume that it i1; shifted to the A position, thereby rendering transmitter-a idle, putting transmitters b and 0 into serv-' ice, and setting the scale cover in the A position, shown in Fig. 10, .to-expose the A scale. At the same time the electrical connections'a're changed as indicated die- I grammatically in Fig. 17, so that transmit ter 6 is connected to the left ear throughrccciver 49, and transmitter c is now connected to the right ear through receiver 50, In cffeet the listener 15 now facing transmitter'a.

Under these conditions the soundn-avc'froni the source '1 reaches transmitter conly a veryshort' interval of time before t reaches transmitter Z), and consequently a very slight niovcnwnt of the compensator from its middle positionv will compensate :t' r'tlns ditfercncc in time. The setting of the co1npcnsator in this position is therefore near the middle as indicated in Fig. 18. In this posilion of the compensator round from a.

source T having a bearing of 50 degrees produccs thesame effect as sound from a source I having abearingot 250 degrees, but

again the listener does not know which is the true bearing and which 18 the false one,

llowever, the hearing of 50 degrees of, the

source T is the same as the hearing; of '1 dctcrinined-in thoC posltiom while the false hearings are different. This result indicates 'to the listener that 310 degrees is the true hearing when he reads upon the A'scale that the bearingni' the sour-cool sound s either 50 degrees or 250 dcgrces.

The fin'a-l atop is-iolshift the transfer switch intothe B position indicated diagrammatically in Fig. 19 to render b transmitter idle, put into service the-transmitters c and a, and expose the B scale, as indicated in Fig.- 11. In the B posit ontrans mitter c is connected through receiver 49 to than the preferred form illustrated.

the left ear of the listener; the reverse of its connection in the A position, while tranza the transmitter a is nearly a maximum. To

compensate for. this great dificren'cein time the compensator must he moved to its ex-' treme position as indicated diagrammath cally in Fig. 19, so that the air pathv from receiver 49 to the left ear of the listener is very long, while the air path from receiver 50' to the right ear of the listener is yery short.

In this position of thecompcnsator.the same effect is produced by sound from source T or from source-F. The true hearing OT is 50 degrees, while the false bearing'OF is 10 degrees, and since the source of sound may he on either-one of these hearings the 13 scale which theoperator reads is graduated so that in this position of the cominittei, a is connected to the-right ear of the pcnroator the bearing is read as either 50 degrees or 10 degrees. The hearing of the source T agrees with the true bearings .determined in the C position and in the [a position, while the hearing of the source F of 10 degrees is a false hearing which does notagrcc with eithcrof the other false bearings determined in the other two positions.- This result proves that the true bearing is 50-degrccs. My invention may be embodied in othfelri transmitters (1-, b and a may hereplaced by underwater.collectors of rubber, or similar material, and the sound transmitted acoustirally to 'the compensator, any two of the collector's beingcoimectedat-w'ill to the inlet ports of the compensator by Valve mech-' anism, such as a rotary valve. @uch a struc tnre isshown in F g. 21 where afgf b' and 0' designate rubber hullos'mountedni'a frame 81 and connected to a rotary v val' v e 83 by tubes 82, 82 and 82. The rotary valve 83 is connected to the compensator 86 by means of the flcxihle tubes 84 and 85. The transfer switch may he made in .various'forin and other changes in details may he madef l',

therefore, do not wish to. he restricted-to the form shown, but. int-endto cover ail changes,

- and modifications within the spirit of my the'scopn. of the appended inventionand claims. c

-W'l.iat I claim as. new and desire to. securchy Lctters'latcnt of the United States,

1. The combination with'twe'sound trans- :nrission systemsfeach composed of an electrical; transmitter l connected ta receiver and otj a flu d; columntthrongh wh ch Q j sound is transmitted; of means; for varying j in said two; systems into vphasejand: thereb pro t I miss and [of an: air path I sound; em tted} system v I l point; to: Zone of another point E v I v niitting= systems mitter connected I plate and e ne a two blocks on the luce' the binaural effect.

The: combination with two sound; trans on systems each composed j of an :ele rial transmitter ;conneetejd to; a receivei for t ansmitting tliei by the receiver,- or mean for lativei lengths of said Iair' the? phase relation of he:

(lent hire;

for ti, n. n1

leach comprising atranso receiver nbmerged "in i osition',' of.

cl receivers nd en deliveredib he compensator II cnmpensatorv oinfprisingg' tn ti ely movable fiati platesfo ne of said lates am t idiebysifie 'lirection j of 'movemen said grooves to divide said grooves into two reflcxed channels, .the length of one of said -channels being increased and that of the other being decreased by rotation of said disk.

7. A compensator comprising twoflat disks mounted to. rotate about a common akis, one of said disks having two pairs of ports'adjacent each other and at (litterent radial distances from the center off said disk, and two projecting blocks in radial alignment, one block between the ports of eachpair, and the other disk havln two grooves concentric with said axis and s aped to fit snugly over said blocks, said grooves extending part way around the disk and' being joined 'by a cross channel at eachend. V

8. A compensator comprising two rela; tively rotatable disks provided with'coopcrating grooves and; arate gair paths inversely relative movement of: said fp latjes, trans j for at will delivering sound: from i j the f relative conditions of; said two fluid i 3 columns jat will'to bring ,oj .an-

' ietmfipen ator, a 3 scale: plate "scales ahdiimov able: jo? slio I rotatjion 1 of said. disks; a scale plate, cover I I I w eiilyonejs ale at ,aj'

niecln n'i'sm; and said: cover to; move: in synch )n in} toi expiosef only that Escalej .WhIClT' itch) 1 1% mechanism 1 the phase: relation disks and.

;variable' in dength I means I i we; three difi'erent poin i gk h i the} i'elatiive r causing saic itching ponds the osition @o'f tit I irnslr :ho'l'dert I .mtqthree nst orusirfon' t aid:

segments I I condbridgmg brush :co-i e other at the a 'eteij iesGll-betl 1th a compensator com rotatable disks 511 in; Inj {the the combina ion I risin two latr'vely:

vided with grooves and cooperating blocks to form two air paths through the compensator variable in length by relative rotation of said disks, twotelephone receivers in comblocks to term." two'sepmunication with the two air paths through the compensator, a comprising threeseginents insulated from one another and means for connecting any one of said segments to one receiver While the adjacent segmentis connected to the other receiver, and three stationary contacts connected through condensers'to said three segments andthrough resistances to a source of current.

11-. The combination with acompens'ator having two separate sound paths relatively variable at will-to alter the phase relation of the sounds in the two paths, sound collectors mounted out of alignment, -1nea'ns for transmitting sound from each of said collectors to'said compensator, means for at will connecting any two of said collectors to the two sound paths through thei'compensator. I 1 I 12. The combination-with a compensator having two separate air paths for sound through it and means for atwill varying the, relative, lengths of said air paths of threesound collectors mounted out of alignz'switching mechanismand I each; colleetoi" to. 'said compensator" indietwo' of'said collectors tp t he twby ivpa hs through-the eon'ip'ensator whe ieby the c m en'satorniay hf'adjusted to br ng the sounds i rom ='a ny= two" collectors; mto' phase "and 1 threetransmittrs-ifioiinted oiit of alignment and electrical connections between said trans initters' and said i-ebiveis may 1 ISii-idtnzinsimlitte reeeive'rswhereby 'f said be'eonnected to any two of 1's, o'f'a compensator for vary ingIt-he' phase-relation of the sounds-emitted saidi-eeeivers' "to bring said sounds into"- b I phase fwlien delivered "by is aid compensator I and thereby-'produ'ee 'the ,binain al' effect;

""14; The I combination with two; i 'e'e'ivers, three-transmitters set out of alignment, elec'-- trical'aeonnection's' between said tifansmitters reeeivers and .a' swit for at will lgonnecting said ieeeivers' to tw'o'of. said 'transmitters',l of a tom the phase'relation of t ensator for varymg e sounds emitted by 'sald'twoj' eeeiversto bring said sounds into phase when delivered'by the eonipensator'. 15.

rotata'ble -disks having f coop ratir g grooves and blocks'vvhich form two air paths variable in length by relative rotation 'ofsaid disks and a vent-for said pathshaving such .a relation between length and bor'efl that "air as pressure is relieved'witliout escape of "sound.

16: The combination 'witli'a telephonic sound transmitting s'ystemeomprisin'ga nicrophone transmitter connected to a re- I ee1ver-" and a battery connected; in ei-rcjuit ail-passage varied v saldmember's, an

with said mie'ropho I I mgand closing said circu t through the miv crophoneaiid' acondenses"shunting j's'ald 'eoher'e'r action in the under :pressuife retained.

tie, of a" switeli for '-openswitch and of 'sufieient 'c ap'aeityto' prevent mi ropho e wl1en' 'sa circuit is opened; I I '3 i 17 A compensator having two nelatively movablame'mbers c'ooperatmg' to form an length by movement of a 'continuouslyopen vent for relieving ail-"pressure in said -passage; ls'aid 'vent'comprisin which is 'adap sound waves.

tedi'to' prevent the escape of 5 18. "A compensator having two relatively .movableinemberscooperatmg to form an airfassage variedlin lengtli by m'ovement of members and a tubular-vent for said passage of such here and length.jthat air Q19; An app arat1is .foi' the ideterihiliation Qf thedirection of travel of vibrations com- I prising t'h nee ioeiiiers of vibrations out. of

a compensator; mea r pplrat ly "to'nnecting: one pair of; the three receivers ssees" I V conneeting-at" will difierent paii's' 0 he combination. with. two rece vers,

on a" diifei'ent pair i A compensator" comprising two "iBliI- tively ga long and narrow passage escapes and sound waves are -tively fixe @7136 'the' eoinpensa'toi "and thereafter opera, tiv'ely connect ng "the I compensator a l'diiferenfi' pair ofith'e three receive 3.

receivers to; the tw o passages through I "compen fi o I 7:. I i 21.- r'llie' Combination of a eonipens havin two separate air passages for s theret iroiig hfand ineansffonv'arying the i -ative lengthsofthe ail pass'ag :Z illl'fBG SOl receivei's mounted out of v ali lenient; means fox-connecting atjwill "one pail of s i "receivers to the-air paths' theeompens' X I of said receivers ties airpaths, so as'to deliver tojthe compen toi'flfsounds icoriresponding l to these re I by one'flof the other of said 'p'giirs ofre were I .L'asdesirledf. f H l "I 1 '22; "Apparatus forthe hinaui'al irlei'flflliliiiay tion of the direction of sound in Wa.te1g,eem prisihgthree spa'eed telephonictransmitters outof line, two ear'pieees ftvve energy mess v. mitting 'c'oni'ijeetin's connected i espeetivelyv at 'oiie 'end tofsa'id'ear ieces, and cdnneet: able respectively atthe other-end first to one *p'airof 'saidtran'sinitters-and than to a disf ferent pai of said transmitters, and means i. for varying the, efiective relative lengths of said energy transmitting'conneetions,

f 23. '-A.ppjaratus for the hinai ral deten'nin-a tion of the directionof travel of soundnesspi'ising'two-air paths for sound, means for! relatively varying the lengthsof said paths; two telephonic receivers, one for eaeh ai1 I 'path to deliver sound thereto; vthree sound 'colleetorsout of alignment (321C111 eompi isingg;

an electrical, telephonio tigmsi'nliter, ax d mean s for successively conneetii'igdifferent pairsof said t two eceivers.

ransniitters 24:. acoustic '1 device consistingfjofa "relatively-fixed and a relatively movable melnbe'r, two paths for sound waves extend" ing. oppositely through ,said device, each path comprisingtwo parallel portions and h'avili'g hoth its inlet andbutlet openings in the"-fiXed' member and" at least a portion of length "in the movable member, so that relative motion of the relatively fixed and movable members causes an equal endinverse'vai iation 'in the lengths of the two 7 passages. o 25. Anacoustic device comprising a rela- I I d memhei-having two inlets for sound and two outlets-for sound-,and a rela- '7- t vely movable member having two opposltely extendingpassageways fon'sonnd each passageway comprising two. parallel pen jtions and afeonne'cting portion,.g ne'o;f the .two parallel; portionsflof each passageway lit lee"

communicating respectively with one of the inlets for sound and the other parallel portion of each passageway communicating respectively with one of the outlets for sound, whereby relative motion of the relatively fixed and movable members causes an equal and inverse variation in the lengths of the two passageways.

26. An acoustic device comprising, a relatively movable member having two parallel passagesways connected together at their op'- posite ends, a. relatively fixed member having twoinlet openings for sound Waves communicating with one of the parallel passageways and two outlet openings for sound waves communicating with the other of the parallel passageways, sound obstructing means in the passageways between the inlet openings and between the outlet openings so as to form two oppositelv extending rebcnt, passages for sound whereby relative motion of the relatively fixed and movable members causes an equal and inverse variation in the lengths of the two sound passages.

27. An acoustic device comprising a fixed and a movable 'member having mutually cngaging surfaces upon which the movable member is slidable with respect to the fixed member, two paths for sound waves extend ing oppositely through said device, each path comprising two pa 'allel grooves inthe.

engaging surface of one of the .n'iembers'f and a passage Connecting said grooves, andlengths of the two paths.

each path having both its inlet and its "outlet in the .fixed member and at'le'aSt a; por-' tion of-it-s length in the movable member; so that relative motion of the two incml'iers causes an equal and inverse variation inthc 28; An acoustic device comprising a iixed and a movable member having mutually engaging surfaces upon which the movable member is slidable with respect to the fixed member; two paths for sound waves extending oppositely through said device, each pathcomprising two parallel grooves in the movable member, and a passage connecting them; two inlet ports for sound and two outlet ports for sound all located inthe fixed member; one of the two parallel grooves of each passageway con'imunicatingrespectively with oneof the inlet ports for sound, and the other parallel groove of each passageway connecting respectively with one of the outlet ports for sound; whereby movement of the movable member causes an equal and inverse variation in the lengths of the two passageways.

29. A compensator comprising a rotatable memberand a fixed member having mutual-' ly engaging surfaces which are maintained in sliding contact as the rotatable member rotates with respectto the fixed member; two channels formed in the engaging surface of one of the n cml'icrs which channels are parallel to the direction of motion oi. the movable member and are connected at their ends by cross-passages; two sound obslruct-' ing means projecting from the engaging surface of the other member and fitting re spectively into the two channels so as to' form two oppositelycxtending rebent passageways; and ports in the member from i which channels'are parallel to the direction of motion of the movable'member and are connected-at their ends by cross-passages;

two sound obstructing means projecting from the engaging surface of the other mom-- her and fitting respectively into the two channels so as to form two oppositely extending rebent passageways; and ports in the member from which the sound obstructing means project, said ports connecting with said channels and located oneon each. sidepf each sound obstructing means.

31.. Apparatus the direction of travel of sound comprising two spaced'telephonic sound collectors, each comprising an electrical transmitter, an elec-' trical connection from each transmitter to a receiver, a fluid path from each receiver, means for relatively varying the fluid paths to vary the -i.'ela'tivo.ti|nc of travel of sound llierethrougli.

32. The combination with a compensator for adjusting the relative lengths of two independent air columns,- of an electrical. telepone system for transmitting sound from one point to one of said air columns and for the determination of fromanother point to the other of said air ers of vibrations forrespectivcl y causing variationsin two electric currents corresponding to the received vibrations, ear pleces, one

'for each earof the observer, energy trans mitting connections between the respective in one or more of such cnnnectiofis whereby the time (if travel fram mic receiver to the corresponding mar piece can be varied with respect to "#310 time of wave} from the Otii7f receiver to its corresponding ear piece.

35. .ippmaius for hiimural determination of the direction of sound in water comprising two spaced electrical telephone transmitters, constituting non-i'esimant receivers of vibrations, twn ear pieces, energy can. be varied transmitting c-rmneciions between th'r: :espec- 'iive-iransmitters and ear pieces, and adjustaoie means in one 01' 1mm 01. such (IUIHIQL? tions wl 'ier'eby the time of travel "from one transmitier 120 the izoii'esgmnding @211" piece with respect to tha time of travei. from the other transmitter to its @011 responding ear piece.

In Wimess 'wiierenf, I have hereunto set my hand this 29th day 03 May 1919.

IRVING LANGM. i TR. 

